The Europa League game between F91 Dudelange and FK Qarabag was delayed when a drone carrying what appeared like a flag has been flown over the pitch.
The incident happened in the first half of this Group A game – which Qarabag won 4-1 – and a delay of more than 15 minutes followed the drones overall look.
The drone carried out a flag appeared to be the contested region of Nagorno-Karabakh.
Dudelange vowed to look into the event and issued a apology.
We apologise to [our] guests from Azerbaijan, the team tweeted. We have nothing related to this provocation. We are going to figure [it] out!
Even though the region is recognised as part of Azerbaijan, its an ethnically-Armenian enclave which came following a battle between the two countries in 1988.
They moved in 1993 to Baku, although qarabag were a team from town of Agdam in Nagorno-Karabakh.
A ceasefire was signed by both countries in 1994 however, the war has never ended – in the area dozens were killed in 2016.
Armenia international Henrikh Mkhitaryan elected not to travel with Arsenal for its 2018-19 final against Chelsea in May to Baku, with hauled out a 3-0 away win over Qarabag in last years group stage.